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    SubjectRe: [RFC][PATCH] irq_work
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    On Fri, Jun 25, 2010 at 5:30 PM, Peter Zijlstra <peterz@infradead.org> wrote:
    >> > You can always miss an NMI since it can always happen before the
    >> > callback gets done, and allowing another enqueue before the callback is
    >> > complete is asking for trouble.
    >>
    >> If we move entry->next = NULL before entry->func(entry), we will not
    >> miss the NMI. Can you show how to miss it in this way?
    >
    > <NMI>
    >  ...
    >  irq_work_queue(&my_work, func);
    >  ...
    > <EOI>
    > <IPI>
    >  irq_work_run()
    >
    >  <NMI>
    >    irq_work_queue(&my_work, func); <FAIL>
    >  <EOI>
    >
    >   my_func.next = NULL;

    entry->func() should follows here. You can collect all information
    (maybe some data in a ring buffer) from NMI handler in entry->func().
    But if you place entry->NULL after entry->func(), you will really lose
    a NMI notification and the information from NMI handler.

    > <EOI>

    > Really not that hard. Now imagine wrapping irq_work in some state and
    > you reusing the state while the function is still running..

    So I suggest to use another flag to signify the function is running to
    distinguish.

    Best Regards,
    Huang Ying
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